Understanding the growth factor requirements specific for transformed (cancer-like) cells may lead to the growth regulation or destruction of these cells. This research proposal calls for the purification of a major component ("Peak III") of the serum growth factor requirement of SV3T3 cells, a mouse fibroblast cell line transformed by an oncogenic DNA virus, Simian Virus 40. Preliminary studies suggest that this growth factor, which specifically affects the growth of SV3T3 and not non-transformed 3T3 cells is an oligopeptide. An investigation will be conducted to characterize the chemical nature of Peak III by determining its possible amino acid, carbohydrate, and lipid content and the chemical constituents necessary for biological activity. In order to uncover the biochemical mechanism of action of Peak III, the cellular mitotic rate, macromolecular syntheses (DNA, RNA, protein), and lipid metabolism will be examined under conditions of Peak III depletion and supplementation. Since unsaturated fatty acids or biotin also limit independently SV3T3 cell growth under these experimental conditions, the possible harmful consequences of such lipid depletion on presumed lipid functions, e.g. membrane nutrient transport, and the restoration of these functions by Peak III and/or unsaturated fatty acids, biotin will also be studied. Finally, attempts will be made to find methods and substances (inhibitor-analogs, active-site blocking agents) which antagonize the action of this transformed cell growth factor.